The joys of living on the DNA cutting edge

It’s a bit disconcerting when your DNA tells you you’re … um … not you.

At least, The Legal Genealogist found it to be so this morning.

There’s a new Tier 1 utility, you see, at GEDmatch Genesis, that allows you to combine your DNA results from multiple testing companies into one super-duper-kit. The idea is that — although there’s a lot of overlap from company to company — the individual testing companies do look at somewhat different places in your autosomes for genealogically relevant markers. So, by combining results, you’d get a more complete set of markers than from any one test.

Think about it this way. Let’s say company A looks at your autosomal DNA — the kind of DNA used in the tests that help us compare our DNA to that of our biological cousins so we can work together to trace our family history1 — in places 1, 2, 3, 4, 5, 8, and 10. And company B looks at places 1, 2, 3, 4, 5, 6 and 7. And company C looks at places 1, 2, 3, 4, 5, 9, and 10. Adding those three kits together would give us a combined look at places 1-10. Pretty cool, huh?

Since I’ve tested with just about everybody under the sun, and I am a Tier 1 GEDmatch user,2 I figured it was worth trying it to see what if any differences there might be between the test results from individual companies and this kind of a super-kit. You can combine tests from four companies so I figured I’d combine results from 23andMe, AncestryDNA, Family Tree DNA and Living DNA.

I hadn’t previously uploaded some of these since I saw no reason to overload the GEDmatch system with that many kits for one person, so I went ahead and did that. And then figured I’d run one-to-one comparisons to make sure I had a good baseline — just what one company might have that another company doesn’t.

First up — looking just at Chromosome 1 — me at Ancestry versus me at 23andMe.

Ancestry and 23andMe

Yup, all that green says I’m me, all right. And the little breaks may suggest where one company has data and the other one doesn’t.3 A total of 621271 SNPs were used for the comparison,4 and 99.997 percent of the SNPs were fully identical.

Next up — again looking just at Chromosome 1 — me at Ancestry versus me at FTDNA.

Ancestry and FTDNA

Yup, still me, all right. This time 631,301 SNPs were used and 99.999 percent were fully identical.

Next up — still looking just at Chromosome 1 — me at Ancestry versus me at Living DNA.

Ancestry and LivingDNA

Um… waitaminnit here. What’s with all that black???

GEDmatch color code

The color code says it means that, comparing 162,427 SNPs… um … there’s no match. “No shared DNA segments found.”

I’m not me?

Okay… maybe it’s the default settings that are causing this. There are different builds — reference sets, called assemblies, issued by the Genome Reference Consortium5 — that can be reported. It was the default that says I’m not me in the graphic above.

So I re-ran it at each setting. The default, Build 37, says I’m not me. But Build 36 says I’m not me. And Build 38 — still not me.

Ditto for a one-to-one comparison between Living DNA and 23andMe. Ditto between Living DNA and Family Tree DNA.

Okay, maybe I downloaded the wrong kit from Living DNA. So I went back and downloaded it again and did a comparison of the files. File name? Check. File size? Check. File contents? Yet another check. No error there; it’s the kit that Living DNA thinks is me.

So… I’m me at three companies, and they all compare one to the other. But at the fourth company I’m apparently not me at all. Nor is the LivingDNA me related in a one-to-one comparison to my sisters or my brothers or…

Um… back to the drawing board here…


Cite/link to this post: Judy G. Russell, “When you’re not you,” The Legal Genealogist (https://www.legalgenealogist.com/blog : posted 7 Apr 2019).

SOURCES

  1. See generally ISOGG Wiki (https://www.isogg.org/wiki), “Autosomal DNA,” rev. 28 Jan 2019.
  2. Which means I pay for access to special tools for DNA analysis. See Kitty Cooper, “New Utilities at GEDmatch: Tier 1 for paid members,” Kitty Cooper’s Blog, posted 20 Oct 2014 (https://blog.kittycooper.com/ : accessed 7 Apr 2019).
  3. Yes, it’s also possible that neither has data in that particular location.
  4. A SNP is a single-nucleotide polymorphism, the “DNA sequence variation occurring when a single nucleotide adenine (A), thymine (T), cytosine (C), or guanine (G) in the genome (or other shared sequence) differs” between two persons. ISOGG Wiki (https://www.isogg.org/wiki), “Single-nucleotide polymorphism,” rev. 30 Nov 2018.
  5. See Helen Lockstone, “A guide to reference genome selection,” 7 March 2017, Oxford Genomics Centre (https://www.well.ox.ac.uk/ogc : accessed 7 Apr 2019).
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